232
ELEMENTS OF MATERIA ME I) 10 A.
America it is met with in various places: that from the shore of SenekaLake in New York is called Seneka oil. Several of the West IndiaIslands, especially Barbadoes and Trinidad, yield it. The Barbadoes petroleum ( Petroleum Barbadense , Ph. Bond. etDubl.: Pisselmim Indicum,Dale) is commonly termed Barbadoes Tar , or B. Naphtha. That importedby Mr. Clarke professes to be the produce of the springs on Mount Hallestate, in Barbadoes . In various localities of Asia, petroleum is metwith in great abundance.
Properties. —Barbadoes petroleum, at ordinary temperatures, has theConsistence of treacle : its colour is reddish brown or blackish; its odourand taste are bituminous. It floats on water: is combustible, yielding athick black smoke, and leaving a carbonaceous residuum. It is insolublein water.
Composition.— The ultimate constituents of Barbadoes petroleum arecarbon and hydrogen, with small quantities of oxygen and nitrogen. Bydistillation, five parts by measure yield rather more than four parts of ayellow oily fluid, somewhat similar iu appearance to the liquid carbo-hydrogen obtained in the manufacture of oil-gas. The residuum inthe retort is a substance analogous to asphaltum. It yields bydestructive distillation traces of ammonia. Some kinds of petroleumcontain paraffine aud eupion.
Physiological Effects. —Petroleum possesses stimulating properties,which are principally observed in its effects on the organs of secretion(the skin, the kidneys, and the mucous membranes), the activity of whichit promotes: hence it has been called sudorific, diuretic, expectorant, &c.It is said to be an excitant to the lymphatic vessels and glands.
Uses. —As an internal remedy it is employed in chronic pulmonaryaffections (as winter coughs, old asthmas, &c.), in obstinate skin diseases(as lepra, psoriasis, and impetigo), and against tape-worm.
As an external agent it is applied to obstinate ulcers, as lupus, and cuta-neous diseases, and is employed as a stimulating liniment in chronicrheumatism, paralysis, and chilblains.
Administration. —The dose of Barbadoes petroleum is a small tea-spoonful given in any convenient vehicle (as some aromatic water, tea, orspirit). The quantity should be gradually increased. It is said that anounce has been taken in the day without inconvenience.
Suc'cinum. — Anther.
History. —Amber was known to Thales of Miletus , (>00 years beforeChrist. He was the first who noticed that when rubbed it acquired thepower of attracting light bodies. Hence arose the term electricity, fromTjXUrpov, amber. Theophrastus (De lapidibus) also mentions this property.
Natural History . —Amber is found in different parts of the world.The principal portion of that met with in commerce, comes from thesouthern coasts of the Baltic, in Prussia, and is cast on the shore betweenKonigsberg and Memel. It is supposed to be disengaged, by the actionof the sea, from beds of lignite.
The vegetable origin of amber is shewn by various facts. It is usuallyassociated with substances (bituminous wood, coal, &c.) known to bederived from plants. Externally we observe on it various impressions ofthe branches and bark of trees; and inclosed in it are insects and